Introduction to IMS

Russ ClarkAugust 18, 2008

IMS Benefits - Official Story• Access Independence - not just Cellular: wired,

WiFi, WiMax, etc

• Standards Based - IP, SIP, portable across providers

• QoS - ability to link application needs to provisioning

• Billing/Charging - for commercial viability, carrier ROI, “one bill”

• Integration of new services - no more stovepipe applications

• presence, location, group management, PoC, voice, text, video

IMS Position

Charging and Billing

No Stovepipes

IMS Architecture

The CSCF

• CSCF - Call Session Control Function

• What IMS calls “The Main SIP Servers”

• Three flavors

• Proxy CSCF

• Interrogating CSCF

• Serving CSCF

The CSCF Family

The CSCF Family

The CSCF Family

IMS Architecture

Other IMS Components

• HSS - Home Subscriber Server

• SLF - Subscriber Locator Function

• PDF - Policy Decision Function

• AS - Application Servers

Subscriber Information

Policy Information

Application Servers

• Presence - user availability and status

• GLM - Group List Management - user groups

• Location - user’s physical location

• PTT - Push To Talk - walkie talkie service

• IM - Instant Messaging - text messaging

• etc, etc, etc